1. Technical Field
Described below is a method for charging material, including lumped carbonaceous (coal-containing) material and (e.g., hot) iron carrier material, into a melter gasifier of a smelting reduction plant.
2. Related Art
In the context of smelting reduction processes for producing pig iron in a melter gasifier, e.g. COREX® or FINEX®, material including carbonaceous material, iron carrier material and fluxes is charged into the melter gasifier. The carbonaceous material is gasified with oxygen to produce a reduction gas, the heat required to melt the iron carrier material being released in the process.
Carbonaceous material includes e.g. coal in lump form or carbonaceous briquettes. It is stored at ambient temperature in a charging bin for carbonaceous material, from which it is loaded into the melter gasifier. In the case of FINEX®, for example, the iron carrier material is hot-briquetted iron (HBI) or hot-compacted iron (HCI). HBI is hot-compacted iron having a very high proportion of metallic iron (often more than 90% metallization) and a density of approximately 5 g/cm3, allowing transport by ship, for example. The material takes the form of individual briquettes, generally >25 mm, and is therefore present in lump form. HCI is hot-compacted iron with fluxes and has a lower proportion of metallic iron than HBI. Its density is slightly less than 4 g/cm3. As part of the manufacturing process for pig iron, HCI is further processed immediately after production, being granulated by crushers and used in a form that is advantageous for a melter gasifier. HCI has a temperature of approximately 550-650° C. in this case. In the case of COREX®, the iron carrier material is e.g. hot direct reduced iron (DRI).
Pyrolysis of coal or carbonaceous briquettes at high temperatures results in the development and release of volatile hydrocarbons and tar. Therefore the carbonaceous material cannot be stored together with hot iron carrier material in a charging bin, since the development and release of volatile hydrocarbons and tar, triggered by the contact with the hot iron carrier material, would result in conglutination and blockages in the charging bin and in the lines transporting the material to the melter gasifier.
The charging of carbonaceous material and iron carrier material into a melter gasifier usually takes place separately in existing related art installations.
Carbonaceous material is transported from e.g. a charging bin for carbonaceous material via screw feeders to a distributing device which is disposed centrally in the dome of the melter gasifier and from which the carbonaceous material is distributed over the cross-section of the melter gasifier as it is introduced into the melter gasifier. Iron carrier material is introduced into the melter gasifier e.g. via a plurality of drop shafts which are arranged around the circumference of the dome of the melter gasifier.
The separate addition of carbonaceous material and iron carrier material into the melter gasifier involves considerable expense in terms of the construction and maintenance of those plant parts required for the separate addition. Moreover, in the case of separate addition, the carbonaceous material and iron carrier material are not distributed with an adequate degree of control on the material bed in the melter gasifier, and e.g. the formation of vertical islands of iron carrier material can occur, thereby adversely affecting the melting and gasification process.
It is known from EP0,299,231A1 to charge the carbonaceous material and the iron carrier material into the melter gasifier centrally via the same opening. Central charging as described in EP0,299,231A1 is disadvantageous in that fresh material is supplied to precisely that region of the material bed which is known as the “dead man” region in the melting and gasification process, wherein preheating and reduction processes take place less effectively than in the peripheral region of the melter gasifier. Moreover, fine and heavy material remains concentrated in the central region of the material bed due to segregation processes, while coarser and lighter material migrates toward the peripheral region. Accordingly, the mixture which is charged onto the material bed is again segregated to some extent and in an uncontrolled manner.